1. Field of the Invention
This invention concerns a coin inspection method and device for inspecting coin genuineness and denomination, and in particular, a coin inspection method and device appropriate for inspection of coins used in vending machines, game equipment and similar.
2. Description of the Related Art
In recent years, the coin inspection devices used in vending machines, game equipment and similar have primarily been electronic coin inspection devices using magnetic sensors which employ induction coils.
This type of coin inspection device generally utilizes the free-fall of the coin, and is configured such that a plurality of induction coils are positioned along the coin pathway guiding a coin which has been inserted from the coin insertion slot. Each of these induction coils is excited at a different frequency to form an electromagnetic field; by the passage through these electromagnetic fields of a coin inserted from the coin insertion slot, the change in the electromagnetic fields is employed to inspect the genuineness and the denomination of the coin.
Coin inspection by a coin inspection device using such magnetic sensors is based on widely-known principles; when a coin passes through the above electromagnetic fields, the amounts of electrical change (change in frequency, change in voltage, change in phase) resulting from the interaction between the electromagnetic fields and the coin are detected, and the genuineness and denomination of the coin are discriminated.
Previously, since coin characteristics are parameters which depend on frequencies; this type of coin inspection device is utilized as a technology which employs a plurality of frequencies to inspect the coin material, outside diameter, thickness and similar, as disclosed in U.S. Pat. No. 3,870,137.
In recent years, coin inspection devices have also been proposed which adopt techniques to detect the surface shape of coins; representative technology has been disclosed in Japanese Patent Laid-open No. H11-167655 and in Japanese Patent Laid-open No. H11-175793.
However, the internationalization of recent years has been accompanied by the easy import of coins from various countries, and there is an increasing number of cases in which such coins are erroneously inserted into vending machines and similar, or are inserted for the purpose of fraud by persons attempting illicit activities.
Among these coins from various countries, some resemble genuine coins in materials, outside diameter, thickness, and other parameters; and, are also rampant large quantities of coins which are coins from other countries, modified so as to resemble genuine coins.
Although such coins from other countries, or modified coins from other countries, have a surface design (pattern of protrusions) different from genuine coins, or have a different coin flange shape, there are nonetheless coins which essentially match in material, outside diameter, and thickness. Hence coin inspection devices using conventional magnetic sensors will sometimes erroneously accept such coins as genuine, and in this case unforeseen damages are incurred by the manager of the vending machine or similar.
Consequently, technology for the precise detection of the pattern of protrusions on the coin surface and the shape of the coin flange is sought.
However, because the coin inspection devices using conventional magnetic sensors are configured to discriminate the genuineness and denomination of the coin being inspected based solely on the peak values and peak positions of detection signal waveforms of magnetic sensors, the amount of information is small, and so there is the problem that coins of other countries, or modified coins of other countries, cannot be reliably discriminated.
An object of this invention is to provide a coin inspection method and device, enabling precise inspection of coins to be inspected, by extracting a large amount of information from sensor detection signal waveforms.
In order to achieve the above object, the invention of claim 1 is a coin inspection method, in which a sensor is positioned along a coin pathway through which a coin passes, and inspection of the coin is performed based on a detection signal waveform of the sensor, comprising the steps of: determining a differential waveform of the detection signal waveform; extracting first information indicating a peak position of the differential waveform, second information indicating a value of the detection signal waveform at the peak position of the differential waveform, and third information indicating a value of the differential waveform at the peak position of the differential waveform; and inspecting the coin by using the first through third information.
The invention of claim 2 is the invention according to claim 1, wherein an output of the sensor is sampled at fixed time intervals and converted from analog to digital values to obtain the detection signal waveform; and differences between adjacent digital values in the detection signal waveform are determined to obtain the differential waveform.
The invention of claim 3 is the invention according to claim 1, wherein when a value of the differential waveform at a time t is xcex94(t), a time point at which a difference between the value xcex94(t) and a value xcex94(txe2x88x922) of the above differential waveform at a time txe2x88x922 which is two sample points previous is zero is extracted as the peak position of the differential waveform.
The invention of claim 4 is the invention according to claim 1, wherein when a value of the differential waveform at a time t is xcex94(t), a time point at which a difference between the value xcex94(t) and a value xcex94(txe2x88x92N) of the differential waveform at a time txe2x88x92N which is N sample points previous is zero is extracted as the peak position of the differential waveform.
The invention of claim 5 is a coin inspection method, in which a sensor is positioned along a coin pathway through which a coin passes, and inspection of the coin is performed based on a detection signal waveform of the sensor; comprising the steps of:
determining a differential waveform of the detection signal waveform; and
inspecting the coin by using, as inspection information, a characteristic quantity of the differential waveform in a specific region.
The invention of claim 6 is the invention according to claim 5, wherein the specific region is a region corresponding to a flange part of the coin.
The invention of claim 7 is the invention according to claim 5, wherein an output of the sensor is sampled at fixed time intervals and a result is converted from analog into digital values to obtain the detection signal waveform, and
differences between adjacent digital values of the detection signal waveform are determined to obtain the differential waveform.
The invention of claim 8 is the invention according to claim 5, wherein the specific region is a region including a zero-cross point-of the differential waveform.
The invention of claim 9 is the invention according to claim 8, wherein the characteristic quantity is a level difference between a height of valley part in the detection signal waveform in the specific region and a height of a peak part adjacent to the valley part in the detection signal waveform.
The invention of claim 10 is the invention according to claim 5, wherein the specific region includes a valley part of the differential waveform, and the characteristic quantity is a ratio of a height of valley part in the differential waveform to a height of a peak part adjacent to the valley part of the differential waveform.
The invention of claim 11 is the invention according to claim 5, wherein the specific region includes a valley part of the differential waveform, and the characteristic quantity is a value of the detection signal waveform corresponding to the valley part of the differential waveform.
The invention of claim 12 is a coin inspection device, in which a sensor is positioned along a coin pathway through which a coin passes and the coin is inspected based on a detection signal waveform of the sensor, comprising:
differential processing means for determining a differential waveform of the detection signal waveform;
information extraction means for extracting first information indicating a peak position of the differential waveform obtained by the differential processing means, second information indicating a value of the detection signal waveform at the peak position of the differential waveform, and third information indicating a value of the differential waveform at the peak position of the differential waveform; and,
inspection means for inspecting the coin based on the first through third information.
The invention of claim 13 is the invention according to claim 12, wherein the differential processing means comprises:
analog-digital conversion means which samples the detection signal waveform of the sensor at fixed time intervals and converts a result from analog to digital values in order to determine detection data corresponding to the detection signal waveform; and
differential data calculation means to determine differential data by calculating the differences between adjacent digital values of the detection data determined by the analog-digital conversion means,
wherein the information extraction means extracts the first information indicating a peak position of the differential data determined by the differential data calculation means, the second information indicating a value of the detection data at the peak position, and the third information indicating a value of the differential data at the peak position; and
the inspection means inspects the coin by using the first through third information extracted by the information extraction means.
The invention of claim 14 is the invention according to claim 13, wherein, when a value of the differential waveform at a time t is xcex94(t), the information extraction means extracts, as the peak position of the differential waveform, a time point at which a difference between the value xcex94(t) and a value xcex94(txe2x88x922) of the differential waveform at a time txe2x88x922 which is two sample points previous is zero.
The invention of claim 15 is the invention according to claim 13, wherein, when a value of the differential waveform at a time t is xcex94(t), the information extraction means extracts, as the peak position of the differential waveform, a time point at which a difference between the value xcex94(t) and a value xcex94(txe2x88x92N) of the differential waveform at a time txe2x88x92N which is N sample points previous is zero.
The invention of claim 16 is a coin inspection device in which a sensor is positioned along a coin pathway through which a coin passes, and the coin is inspected based on a detection signal waveform of the sensor, comprising:
differential processing means for determining a differential waveform of the detection signal waveform; and
coin inspection means for inspecting the coin, using, as inspection information, a characteristic quantity in a specific region of the differential waveform determined by the differential processing means.
The invention of claim 17 is the invention according to claim 16, wherein the specific region is a region corresponding to a flange part of the coin.
The invention of claim 18 is the invention according to claim 16, 18. The coin inspection device according to claim 16, wherein the differential processing means comprises:
analog-digital conversion means which samples an output of the sensor at fixed time intervals and performs analog-digital conversion to obtain the detection signal waveform; and
differential waveform calculation means which determines the differential waveform by calculating the differences between adjacent digital values in the detection signal waveform obtained by the analog-digital conversion means.
The invention of claim 19 is the invention according to claim 16, wherein the specific region is a region containing a zero-cross point of the differential waveform.
The invention of claim 20 is the invention according to claim 19, wherein the coin inspection means inspects the coin, using, as the inspection information, a level difference between a height of a valley part of the detection signal waveform corresponding to the specific region of the differential waveform, and a peak part adjacent to the valley part of the detection signal waveform.
The invention of claim 21 is the invention according to claim 16, wherein the specific region is a region including a valley part of the differential waveform, and
the coin inspection means inspects the coin, using, as the inspection information, a ratio of a height of the valley part of the differential waveform to a height of a peak part of the differential waveform adjacent to the valley part.
The invention of claim 22 is the invention according to claim 16, wherein the specific region is a region including a valley part of the differential waveform, and
the coin inspection means inspects the coin, using, as the inspection information, a value of the detection signal waveform corresponding to the valley part of the differential waveform.
According to this invention, changes in the output signal waveform of the sensor can be examined in detail by a simple method, whereby the characteristics of each coin can be detected precisely, and problems in coin selection can be prevented.